Removable trunnion for piston and cylinder devices



A ril 11, 1961 F. s. FLlCK ET A1. 2,979,369

REMOVABLE TRUNNION FOR PISTON AND CYLINDER DEVICES Filed May 31, 1960 2 Sheets-Sheet 1 April 11, 1961 F. s. FLlCK ET AL 2,979,369

REMOVABLE TRUNNION FOR PISTON AND CYLINDER DEVICES Filed May 31, 1960 2 Sheets-Sheet 2 FIEE] REMOVABLE TRUNNION FOR PISTON AND CYLINDER DEVICES Francis S. Flick, Oak Park, and Walter J. Kudlaty, Elmhurst, Ill., assignors to Flick-Reedy Corporation, a corporation of Illinois Filed May 31, 1960, Ser. No. 82,899

8 Claims. (Cl. 309-2) This invention relates to a mounting for a piston and cylinder device, and more particular to a removable trunnion mounting having means to accurately secure removable trunnion pins on opposite sides of the device for forming the trunnion axis.

In the past, trunnion mountings for piston and cylinder devices have been primarily of the non-removable type. These mountings had trunnion pins secured to the device by welding. A few varieties of removable trunnion pins have been developed which are adapted to fit into a simple cylindrical socket in the head of the cylinder device. Many of such removable pins have/proved to be quite unsatisfactory. Some undesirable characteristics of such pins were that the sockets were unable to assure accurate concentricity and squareness of the pins to the intended trunnion axis, the trunnion axis was not accurately located with respect to the cylinder device, and the pins developed the tendency to rotate in place during pivotal movement of the device.

The principal object of this invention is to provide a new and improved trunnion mounting for a piston and cylinder device.

Another object is to provide an improved trunnion mounting for a piston and cylinder device having removable trunnion pins secured to sockets or cavities on opposite sides of the device, the trunnion pins and cavities cooperating to assure concentricity and squareness of the pins with the intended trunnion axis.

A further object is to provide an improved trunnion mounting for a piston and cylinder device having removable trunnion pins which can be releasably locked against rotation when mounted in cavities in the device.

A further object of this invention is to provide an improved trunnion mounting for a piston and cylinder device having removable trunnion pins mounted in cavities in said device wherein cooperating surfaces serve to maintain concentricity and squareness while at the same time providing large bearing areas to withstand the bearing Figure l is a top plan view of the piston and cylinder device having a removable trunnion mounting structure of this invention secured to opposite sides of the cylinder head or cap;

Figure 2 is a side elevational view of a portion of the piston and cylinder device of Figure 1 turned 90 therefrom;

Figure 3 is an enlarged central sectional view through one of the trunnion pins separate from the piston and 2,979,369 Patented Apr. 11, 1961 EQC cylinder device and illustrating a step in the manufacture of the pin;

' Figure 4 is an enlarged fragmentary central sectional view of the pin shown in Figure 3 illustrating a further step in the manufacture of the pin;

Figure 5 is anenlarged fragmentary elevational view of one of the completed trunnion pins;

Figure 6 is an enlarged fragmentary sectional view taken through the head of the piston and cylinder device illustrating one of thecavities for receiving a trunnion r Figure 7 is an enlarged fragmentary sectional view taken substantially as indicated along line 77 of Figure 2 through one of the trunnion pins;

Figure 8 is an enlarged fragmentary sectional view of the pin illustrated in Figure 3;

Figure 9 is an end view of the trunnion mounting taken substantially as indicated along line 99 of Figure 7; and

Figure 10 is an enlarged sectional view of a portion of the piston and cylinder device and trunnion mounting showing the removal of a trunnion pin from its cavity.

In the embodiment illustrated and as shown in Figure 1 a fluid operated piston and cylinder device, generally designated 10, is provided with a trunnion mount, generally designated 11, for pivotally mounting the cylinder for swinging movement about one-end during operation of the device. The trunnion mount comprises cylindrical trunnion pins 12 secured in shallow sockets or .cavities 13 (Figure 6) on opposite sides of the cylinder head forming a trunnion axis 14 transverse and normal to the center line 24 of the cylinder. The pins may be located as desired, in the head, cap or between the head and cap on conventional bars used for this purpose. The protruding free ends of the trunnion pins are intended to rest in bearings provided for that purpose in machinery or the like Withwhich the piston and cylinder device is to be used. A novel arrangement of mating surfaces on the pins and in the cavities guarantee accurate alignment of the'trunnion mount. Also, a novel construction is employed to lock the trunnion pins against rotation during use and yet permit removal of the pins and reassembly for further use.

This invention is applicable to all types of piston and cylinder devices having a head or other structure in which shallow cavities may be formed for receiving the trunnion pins. The piston and cylinder device of the present embodiment comprises a cylinder tube 15 with a head at each end, herein shown as a cap 16 and a head 17 against which a piston rod bushing retainer plate 18 bears. The cylinder tube ends are sealed to the heads as by the use of a flexible sealing material 19 (Figure 6). A plurality of tie rods 20 pass thrtough the heads and are provided with nuts 21 hearing on the outer surfaces of the cap and plate for holding the parts in assembled relation as illustrated in Figure l. A'p-iston withinthe cylinder tube (not shown) is mounted on one end of a piston rod 22 and a device to be moved (not shown) is attached to the opposite end of the rod. The rod reciprocably operates through a bushing in the head. Hydraulic fluid for moving the piston within the cylinder may be admitted to either side of the piston through conduits 23. threadably connected to ports in the head and cap respectively. a

Accurate mounting of the trunnion pins has been diflicult to achieve and even more difficult to maintain as loads are applied repeatedly by the cylinder device on which the trunnion pins are mounted. The present invention solves these prior problems by novel structure that maintains each pin :on a predetermined center line relative to the cylinder even against intermittent loading tending to loosen the pins.

A cavity 13 is formed on each opposite side of the cap 16 to removably receive a trunnion pin, each cavity being located with extreme precision relative to the piston and cylinder device. As shown in Figure 1, the cavities are concentrically aligned with the center line 14 common to each cavity and the center line forms the trunnion axis. The center line 14 extends transversely through and normal to the center line 24 of the piston and cylinder device in order to locate the trunnions on the center line 14 and thereby prohibit side loading effects during pivotal operation of the device.

Each cavity has a plurality of accurately machined surfaces forming stepped walls. Referring to Figure 6, and proceeding inwardly from the outer surface of the cap, there is illustrated a cylindrical bore having a circular cylindrical surface 25 concentric to the common center line 14. At the inner end of surface 25 is an annular flat surface 26 lying in a plane normal to the common center line 14, and extending radially from the inner end of the surface 25 to. form a step in the cavity. Another circular cylindrical bore concentric to the common center line, hereby termed the concentric surface, extends inwardly of the cavity from the smaller circumference of the surface 26. The construction of concentric surface 27 is intended primarily to assure exact concentricity of the trunnion pins with the common center line 14, whereas the surface 26 is constructed primarily to assure accurate squareness of the trunnion pin entirely throughout its length with the common center line. These surfaces enable precise tolerances to be maintained with mating surfaces so that exact pin position is achieved. The bottom of the cavity has a flat annular surface 28 generally normal to the center line 14 and which forms a last step in the cavity. A threaded bore 29 extends inwardly of the cap on the center line 14 to receive a standard machine screw.

The cavity described is intended to mount a removable trunnion pin having surfaces to mate with the accurate surfaces in the cavity. The pins are formed as illustrated in the drawings. Turning now to Figure 3, there is shown a trunnion pin 12 in a partially completed stage of manufacture. Each pin is formed from a suitable length of circular cylindrical metal stock which is provided with a threaded bore 30 extending centrally through the pin, and aligned with an enlarged recess portion 31 forming a step having a fiat annular shoulder 32 against which a machine screw head may bear. The threaded bore of the pin is slightly larger in diameter than the diameter of the threaded bore 29 in the cylinder cap '16 in order to accommodate a large machine screw used to remove the pin which will be subsequently described. The shoulder 32 in the pin is at the inner end of the enlarged recess portion 31 and may provide bearing for the head of another machine screw used to secure the pin in the cavity.

A plurality of annular machined surfacm is provided at the inner end 33 of each pin to mate with the stepped walls of the cavities. Proceeding from the lower end of the pin, as shown in Figure 3, the plurality of surfaces comprise a flat annular end 34; a circular cylindrical surface 35, designated herein as the pin concentric surface, which surface is concentric with the center line of the trunnion pin and extends longitudinally from the periphery of the bottom surface; an annular flat shoulder 36 normal to the pin center line and extending radially outwardly to form a shoulder for face to face engagement with the surface 26 in the cavity; and a circular cylindrical surface 37, lying concentric with the pin center line and extending about the pin adjacent the outer end of the normal surface 36 for mating with the surface 26 in a cavity of the cylinder cap. The surface 37, as shown in Figure 3, is slightly smaller in diameter than the balance of the pin in order that the knurl to be put thereon will not project outwardly beyond surface 38. The outer surface of the pin is a circular cylindrical surface 38 constituting the journal surface of the trunnion pin engageable in journal bearings. The journal surface 38 is given a hard finish, preferably chrome plating.

In Figure 4, the surface 37 is fully knurled to form a gripping area 39 resulting in the expansion of its periphery radially outward to a diameter slightly less than the diameter of the journal surface 38. The knurled surface should not have a diameter greater than the journal surface in order to permit insertion of the trunnion pins through the bearings used to support the device. The knurled surface is designed to be press-fitted into engagement with the smooth cooperating surface 25 of the cavity and thereby create an interference lock which secures the pin against turning or loosening. An inner portion of the knurled surface is machined to provide a sloping nose portion 40 which will aid in guiding the pin into one of the cavities. It is important that the knurl be removed at the leading edge so as to avoid moving metal ahead of the knurl as the pin advances into the cavity, thus avoiding any interference with the mating of surface 36 on the pin with surface 26 in the cavity. The nose portion 40 includes a conical surface 41 between the smaller smooth surface 42 and the full sized knurled surface 39. The depth of each cavity is preferably adapted to receive a trunnion pin so that the trailing edge of the pin gripping surface 39 fits flush with the outer surface of the cylinder head cap or other supporting structure.

The surface 27 in the cavity and adjacent surface 26 i normal thereto are intended to mate respectively with the surface 35 and shoulder 36 on the pin when the inner end of a trunnion pin is inserted into a cavity. The engagement of the mating surfaces will pilot the pin into concentricity with the intended trunnion axis as located by the cavities. In addition, the mating surfaces are adapted to bear the expected loads placed upon the trunnion mount. The full engagement of the surface 26 of the cavity with the surface 36 on the pin brings the pincenter line into coincidence with the intended trunnion axis. The knurled surface 39 on the pin when in engagement with the surface 25 of the cavity prevents the pin from turning or loosening during loading. As best shown in Figure 10, a portion of the surfaces 26 and 27 engage and align the pin before the knurled surface begins to enter the cavity, insuring accurate pin positioning.

To secure the trunnion pins to the cylinder cap 16, a cap screw 43 with a hex recessed drive head is used which extends loosely through the trunnion pin to be threadably received by the threaded bore 29 at the bottom of the cavity (Figure 7). The hollow head of the screw 43 is hexagonally shaped to receive a standard wrench bit (not shown) and fits entirely within the enlarged stepped recess 31 of the pin bore to lie flush with the outer end 44 of the trunnion pin. The under-surface of the screw head bears against the shoulder 32 when the screw 43 is fully inserted into the trunnion pin to draw the pin into the cavity.

A further feature of the invention is the ease with which a trunnion pin may be removed from assembly in the cavity. In Figure 10, a large-sized machine screw 45 having a conventional hexagonally-shaped head is threadably received by the central bore 30 of the trunnion pin. The shank of the screw 45 is turned entirely through the pin bore so as to have its spherically-shaped end 46 engage the edge 47 of the threaded opening 29 at the bottom of the cavity. Turning of the screw 45 in place while engaged with the cavity bottom and in a direction so as to move it further into the pin, forces the trunnion pin upwardly along the screw shank and out of the cavity.

The trunnion pins may be easily installed in the cavities by placing the inner end 33 of a pin into one of the cavities so that the mating concentric surfaces have engaged and the conical surface 41 of the knurled surface nose portion has come into engagement with the rim of the cavity. The pin may be driven into place and secured by the machine screw. If desired, a scribe line may be marked on the pin and adjacent cylinder head so that the pin may be removed and thereafter replaced in the same position previously occupied.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, for some modifications will be obvious to those skilled in the art.

We claim: 7

l. A removable trunnion mount for a piston and cylinder device, comprising: a head on the piston and cylinder device having cavities on opposite sides thereof to removably receive trunnion pins, said cavities being concentric with a common center line perpendicular to the center line of the cylinder, each cavity having walls forming a pair of adjacent surfaces, one concentric with said center line and the other normal to said center line; a pair of trunnion pins having inner ends adapted to enter said cavities, said pins each having a longitudinal axis and a pair of surfaces on the inner end of the pin respectively concentric with said axis and normal to said axis, said concentric surface on said pin being positioned to engage the concentric surface in the cavity when the pin is assembled in said cavity to maintain the inner end of the pin axis on said common center line, said normal surface on said pin being positioned to engage said normal surface in said cavity upon said assembly to maintain the pin axis coincident with said common center line; and removable means for securing the pins to the cylinder head in assembled relation therewith.

2. A removable trunnion mount for a piston and cylinder device, comp-rising: means on the piston and cylinder device having opposite cavities to respectively receive a trunnion pin, each cavity having a center line common to both cavities and normal to the center line of the piston and cylinder device, each cavity having a pair of surfaces forming walls thereof, one being circular cylindrical and concentric to the common center line and the other being perpendicular to said common center line, and a pair of pins, one for mounting in each cavity, said pin having surfaces for mating with said surfaces forming walls in said cavity so that the concentric mating surfaces maintain the pins concentric with said center line and the other mating surfaces hold the pin square with the center line of the cylinder.

3. A removable trunnion mount for a piston and cylinder device, comprising: a head on the piston and cylinder device having cavities on opposite sides to removably receive trunnion pins, each head cavity being aligned on a common center line perpendicular to the center line of the cylinder and having a circular cylindrical surface concentric with said common center line; an annular flat surface at the one end of each said cylindrical surfaces forming therewith a step in each cavity with the flat surface lying in a plane normal to said common center line; a pair of hollow trunnion pins, one for each cavity, each pin having a longitudinal axis and a circular cylindrical surface at its inner end to mate with the circular cylindrical surface in said head cavity to hold said pin concentric with said common center line upon assembly of the pin into the cavity; and a shoulder on said pin lying in a plane normal to the pin axis and positioned to engage said flat surface in said cavity to align the axis of the pin on said common center line; and

means removably securing the trunnion pin to said cylinder head with said mating and engaging surfaces in contact holding the trunnion pin in proper position on the cylinder he ad.

4. A removable trunnion mount for a piston and cylinder device, comprising: a head on the piston and cylinder device having cavities 'on opposite sides thereof to removably receive trunnion pins, said cavities being concentric with a common center line extending transversely through the center line of the cylinder, each cavity having an annular step therein including a cylindrical sur- '6 face concentric with the common center lineand a flat surface normal to the common center line; a pair of trunnion pins having inner ends adapted to enter said cavities, said pins each having a longitudinal axis and an exterior annular step on the inner end of the pin, said step on the pin including a cylindrical surface concentric with the pin axis and a flat surface normal to the pin axis, said step on the pin being positioned to engage the step in the cavity when the pin is assembled in said cavity for maintaining the inner end of the pin axis on said common center line and for maintaining the entire pin axis coincident with the common center line; means on each of said trunnion pins for engagement with a wall of one of said cavities to frictionally lock saidpin invplace when assembled in said cavity and prevent turning or loosening of the pin during loading; and removable means for securing the pins to the cylinder head in assembled relation therewith.

5. A removable trunnion mount for a piston and cylinder device, comprising: a head on the piston and cylinder device having cavities on opposite sides thereof to removably receive trunnion pins, said cavities being concentric with a corrnnon center line perpendicular to the center line of the cylinder, each cavity having an annular step therein including a cylindrical surface concentric with the common center line and a flat surface normal to the common center line; a pair of trunnion pins having inner ends adapted to enter said cavities, said pins each having a longitudinal axis and an exterior annular step on the inner end of the pin, said step including a cylindrical surface concentric with the pin axis and a flat surface normal to the pin axis, said step on the pin being positioned to engage the step in the cavity when the pin is assembled in said cavity for maintaining the inner end of the pin axis on said common center line and for maintaining the entire pin axis coincident with the common center line, said pins each having a knurled annular surface adapted to frictionally lock with a portion of the cavity when the pin is fully assembled in said cavity to prevent turning or loosening of the pin therein under load.

6. The removable trunnion mount of claim 5 wherein each said trunnion pin has a central bore with a stepped recess forming an annular shoulder lying in a plane normal to the axis of said pin, each said cavity having a threaded central bore extending inwardly of the cylinder head from the bottom of the cavity; and a machine screw is threadably received by said threaded central bore in the cap and extends loosely through said pin central bore having its head bearing inwardly against said annular shoulder on said pin to secure said trunnion pin within said cavity with the mating surfacesof said pin and cavity fully engaged.

7. The removable trunnion mount of claim 6 in which said pin central bore is threaded to threadably receive a machine screw therein adapted to engage the bottom of the cavity for removing said frictionally locked pin from said cavity, said machine screw having a sufliciently elongated shank to extend fully through said pin central bore and engage the cavity bottom while having its head spaced from the outer end of the pin.

8. A removable trunnion mount for a piston and cylinder device, comprising: means on the piston and cylinder device having cavities on opposite sides to removably receive the trunnion pin, each cavity being aligned on a common center line perpendicular to the center line of the cylinder and having a circular cylindrical side Wall concentric with said common center line; a step in each cavity adjacent the bottom of the cavity including said circular cylindrical surface and an 7 a longitudinal axis and an exterior annular step at its inner end to mate with the step of said cavity, each said step on the pin comprising a circular cylindrical surface adapted to mate with the concentric surface in said cavity to hold said pin concentric with said common center line upon assembly of the pin into the cavity and a shoulder lying in a plane normal to the pin axis and positioned to mate with said flat surface in said cavity to align the axis of the pin on said common center line, a circular cylindrical knurled surface on the pin concentric to said pin axis, said cavity having a side wall to receive the knurled surface, the latter having a diameter slightly larger than the diameter of the cavity side wall, and being adapted to frictionally lock with said cavity side wall when the pin is pressed into said 15 2,349,263

10 draw the trunnion pin tightly Within the cavity.

References Cited in the file of this patent UNITED STATES PATENTS Johnston Aug. 26, 1958 

